Manufacture of artificial silk



Aug. 25, 1942. H. D. MULLER MANUFACTURE OF ARTIFICIAL SILK Filed March 18, 1940 2 Sheets-Sheet l Am. 25, 19426 H. D. MULLER MANUFACTURE OF ARTIFICIAL SILK Filed March 18, 1940 2 Sheets-Sheet 2 Patented Aug. 25, 1942 MANUFACTURE OF ARTIFICIAL SILK Hendrik David Muller, Liverpool, England, as-

signor to American Enka Corporation, Enka, N. 0., a corporation of Delaware Application March 18, 1940, Serial No. 324,727 In Great Britain May 5, 1939 2 Claims.

This invention relates to improvements in the manufacture of viscose artificial silk. Threads of artificial viscose silk which are very strong both in the dry and wet state have hitherto been produced for example by passing the spinning solution into very strong acid baths or by subjecting the freshly spun threads to considerable stretching. The stretching operation has been assisted by passing the thread during stretching through a warm bath containing salt and acid, e. g. through a dilute spinning bath solution or through hot water. In either case a considerable stretching of the thread is essential in order to produce the desired result, but this high stretch may easily give rise to certain defects in the finished thread.

It is therefore the object of the present'invention to provide a process which avoids these defects by carrying out the stretching of the thread in a. particular manner.

It is a further object of the invention to provide a process for the production of threads of viscose artificial silk which is capable of being employed in conjunction with spinning centrifuges or with spinning bobbins.

According to the present invention there is provided a process for the manufacture of viscose artificial silk which includes the step of stretching the freshly spun thread before it is collected in at least three stages by means of rotary stretching devices and treating the thread with liquid at an elevated temperature during one of the stretching stages. The thread may be stretched while in the liquid by an amount not greater than 45% of its length.

The rotary stretching device may conveniently consist of two rollers rotating at increasing peripheral speeds and one form of such a device may c ns st of a stepped roller, the thread being passed first over that part of the roller of smaller diameter and thence around a guide pulley and over that part of the roller of larger diameter.

In one application of the invention the thread may be subjected to treatment with a liquid bath at an elevated temperature during the second stretching operation and in such a process the thread passing from the spinning nozzles into the precipitation bath may be subjected to initial stretching by means of two rollers rotating at increasing peripheral speeds and may thereafter be guided from the second roller in a downward direction around a guide roller in a bath containing liquid at an elevated temperature and thereafter in an upward direction to a second pair of stretching rollers.

The peripheral speeds of thread takes place.

the first and second pairs of rollers are so adjusted that the thread is also stretched while passing through the liquid bath between thepairs of rollers.

The bath in which the stretching takes place is maintained at a temperaturebetween 40 and 90 C. Thus according to circumstances it may conveniently have a temperature of 40, 50, or C. The liquid may contain relatively small quantities of a salt and acid, for example sodium sulphate and sulphuric acid and may contain in addition smaller amounts of the sulphates of magnesium and zinc.

In order to simplify the apparatus, stepped rollers may conveniently take the place of rollers rotating at increasing peripheral speeds. The number of stretching operations may be increased to four, five or more and the individual stepped rollers themselves may be arranged so that each of the stretching operations takes place in a number of steps and the degree of stretching which takes place at any particular stage of the whole process may thus be regulated and predetermined according to the final stretch desired.

Instead of providing a single guide roller for the liquid bath a number of guide rollers around 'which the thread passes in series may be provided in order that the time of contact of the thread with the liquid may be increased.

By use of the present invention viscose artificial silk thread may be stretched to a high degree without danger of introducing defects into the thread.

The invention may be more readily understood and: appreciated by reference to the following drawings wherein Figure 1 is a diagrammatic view of a viscose spinning system showing the essential parts of an apparatus used in the centrifugal spinning process;

Figure 2 shows diagrammatically a viscose spinning system adapted for the bobbin spinning process;

Figure 3 is a diagrammatic view'of a stepped roller construction that may be employed in either of the systems exemplified in Figures 1 or 2; and

Figure 4 is of a view in end elevation of a driving means suitable for the actuation of the stepped rollers.

Referring now to Figure 1, the thread l0 leaving the spinning bath I I passes over the lower step I2 of the first stepped roller and thence around the guide roller [3 and over the larger step M of the roller whereby stretching of the The thread then passes in a downward direction and is guided around a small guide pulley i5 in the bath i6 which contains liquid at elevated temperature. From this bath the thread passes to the stepped roller IT, IS which is driven at such a speed that stretching of the thread takes place between the stepped rollers l2, l4 and I1, I8. also takes place in passing from the lower step ll of the stepped roller around the guide roller l9 and over the step l8. After this stretching the thread is passed in the downward direction into the spinning pot 28.

- The means for driving stepped rollers l1, I8 at a greater speed than stepped rollers I2, I 4 so as to cause stretch between roller l4 and roller I1 is shown in Figure 4. The driving arrangement Stretching of the thread per se forms no part of this invention and is of the type described in the prior art.

Bothstepped rollers may be driven from a common shaft 39 actuated by a source of power, not

shown. Shaft 39 is provided with two bevel gears 40 and 4| which through intermediate gear trains drive stepped rollers I1, l8 and I2, I4 respectively. Bevel gear 4| meshes with bevel gear 42 mounted 'on a shaft 43'which likewise carries a gear 44.

' carrying a bevel gear 54 meshing with'a bevel gear 55 carried on a stub shaft 56 which also carries'stepped'rollers l2, l4. Gear 58 is carried on the end of a slotted arm 51 of a bell crank 58 pivotally mounted at 59 and held in position by a lock nut 68. The shaft of gear 5| passes through the slot in arm 51 so that bell crank 58 may be moved to difierent positions to 'allow for easy replacement of gear 50 by a similar gear of different diameter. Thus the speed of stepped rollers |2, |4 may be varied by a change in the diameter of the gear 58 as well as by a change in the diameter of the gear 45.

Stepped rollers l1, l8 are driven through a gear train from bevel gear 48 on shaft 39, gear 48 meshing with a gear 6| which is attached to a shaft 62 having at its other end another bevel gear 63. Bevel gear 63 drives a gear 64 mounted on a shaft 65 which is additionally provided with a gear 66. Gear 66 meshes with a gear 61 mounted on a shaft 68 anchored to the end of an arm of a bell crank 69 which is mounted for pivotal movement about shaft 65, and may be held in adjusted angular position by a lock nut 10. Gear 61, because of its disposition on an arm of hell crank 69, may be replaced by a similar gear of different diameter and will thus serve to increase or decrease the speed of a gear mounted on a shaft 12 which carries additionally a bevel gear 13 meshing with bevel gear 14 on stub shaft 15 to which stepped rollers I! and I8 are attached.

As shown, it is contemplated that gear 61 be of a size to cause stepped rollers |8 to rotate at a higher speed than rollers I2, I 4.

It will be understood that slipping of the thread on the surfaces of the stepped rollers may be prevented by passing the thread more than once around each step of the roller.

Figure 2 shows the essential features of the apparatus when arranged for the spinning of viscose artificial silk by a bobbin spinning process.

As in Figure 1, the thread 2| is spun in the spinning bath 22 and thence passes over the stepped rollers 23. 24 and the guide roller '25 and thence round the roller 26 in the liquid bath 2! to the stepped rollers 28, 29 and guide roller 30. From that stage the thread passes around the guide roller 3| and thence to the bobbin 32 via the winding device 33. The peripheral speed of the spinning bobbin may be smallepthan, equal to or larger than that of the step 29 but it will be understood that in any case the speed at which the thread is woundon the bobbin 32 must be greater than the peripheral speed of the step 28.

Figure 3 shows a stepped roller which is mounted on a driving shaft 34 and comprises two integrally mounted steps 35 and 36. The thread 31 runson to the lower... step 35, thence over the guide roller 38 and from the guide roller over the higher step 36.

Although the thread is not in general stretched in the liquid by an amount in excessof 45% the present process permits of a high total degree of stretching and this ensures a very considerable Example I A viscose solution containing 7% cellulose and 6% alkali and having a degree of maturity corresponding to a Hottenroth number of 12 is spun in a centrifugal spinning'machine of the general The artificial silk has,

type shown in Figure 1. a denier of 120 and is spun from spinning nozzles I having: 40 holes'each 0.08 mm. in diameter. The

spinning bath consists of an aqueous solution' containing:

' I Grams Sulphuric acid per litre Sodium sulphate per litre 250 Magnesium sulphate per litre 40 Zinc sulphate per litre 15 The thread l0 leavin the spinning bath first passes over a stepped roller |2 which takes up the thread at the rate of 34.9 m. per minute and the step I4 of the roller passes it On at the rate of 38.2 m. per minute, thus efiecting a stretching of 9.5%. The thread then passes around a small freely turning guide roller 5 mounted'in a bath l6 which is maintained at a temperature of 70 C. and containing 10 gms. sulphuric acid and 20 gms. sodium sulphate per litre in addition to small quantities of magnesium sulphate and zinc sulphate and thence passes to a second stepped roller H which takes up the thread at the rate of 51.3 in. per minute. While the thread passes through the bath IE it is thus subjected to a stretching of 34%. In passing from roller 11 to roller |8 the thread is stretched by a further 17% and it leaves the roller I8 at the rate of 60 in. per minute and passes to the spinning pot 20.

Example II A viscose solution containing 7'7 cellulose and 7% alkali and having a degree of maturity equal to a Hottenroth number of 11 is spun in a spinning bath having the composition:

Grams Sulphuric acid per litre j Sodium sulphate per litre 230 Magnesium sulphate per litre 70 Zinc sulphate per litre 10 The spinning nozzle has a 100 holes each 0.07

mm. in diameter and the artificial silk thus formed has a denier of 250.

Referring to Figure 2 the thread 2| leaving the spinning bath 22 first passes over a stepped roller 23, 24 which takes up the thread at 40 m. per minute and passes it on at 44.5 m'. The thread then passes around the roller 26 in a bath 21. This bath contains gms. of sulphuric acid and -gins. sodium sulphate per litre in addition to small quantities of magnesium sulphate and zinc sulphate and is maintained at a temperature of 70 C. After leaving the bath the thread passes around a second stepped roller 28, 29 which takes up the thread at the rate of 60.3 in. per minute, the step 29 of the roller having a peripheral speed of 72 m. The thread is Wound on the spinning bobbin 32 at the rate of '70 in. per minute.

Example III Viscose artificial silk is prepared from a solution having a composition similar to that described in Example I. After passing through the bath l6 which contains 20 gms. sulphuric acid and 40 gms. sodium sulphate per litre in addition to small quantities of magnesium sulphate and zinc sulphate and which is maintained at 75 C., the thread is finally taken up in a spinnin pot 20 (Figure 1).

Example IV Viscose artificial silk is prepared in the manner described in Example II, but the bath 2! is maintained at a temperature of 65 C. and contains 50 gms. of sulphuric acid and 80 gms. sodium sulphate per litre in addition to small quantities of magnesium sulphate and zinc sulphate.

What is claimed is:

1. A process for the manufacture of viscose artificial silk which comprises extruding a viscose solution through minute orifices into a, coagulating bath to form filamentous thread therefrom, drawing the thread from the bath and stretching the same by passing the thread around surfaces driven at different peripheral speeds, passing the thread through a liquid bath maintained at a temperature in a range of about C. to about C. and again stretching the thread during said passage, effecting a third stretching operation by passing the thread around surfaces driven at different peripheral speeds and finally collecting the thread.

2. In an apparatus for the manufacture of viscose artificial silk thread, including a spinning nozzle, a coagulating bath and a collecting device, the combination which comprises a driven stepped roller located adjacent the coagulating bath for initially stretching the thread as it is propelled therearound from the step of smaller diameter to which the thread is delivered from the coagulating bath to the step of larger diameter, means for guiding the thread from the step of smaller diameter to that of greater diameter, a second driven stepped roller for stretching the thread as it is propelled therearound from the step of smaller diameter to the step of greater diameter, means for guiding the thread from the step of smaller diameter to the step of greater diameter on said second roller, means for guiding the thread from the step of greater diameter of the first roller to the step of smaller diameter of the second roller, means for driving the step of smaller diameter of said second roller at a higher rate of speed than the step of larger diameter of said first roller, a treating bath positioned between said stepped rollers and means located within said treating bath for guiding the thread therethrough, said means'being the guide means by which the thread is led from the first stepped roller to the second stepped roller whereby a three-stage stretching operation may be performed by the use of two stepped godets.

HENDRIK DAVID MULLER. 

